Preparation of vinyl carbamates

ABSTRACT

Vinyl carbamate compounds are prepared by reacting appropriate secondary amines with carbon dioxide and acetylenically unsaturated compounds in the presence of a compound of a metal from the platinum group, in particular a ruthenium compound, with either one of the two process steps (a) and (b) or, preferably, both being carried out: 
     (a) the acetylene compound is reinjected during the reaction; 
     (b) the reaction is carried out in the presence of a tertiary amine.

This application is a national stage filing under 35 USC 371 and wasbased upon PCT International Application No. PCT/EP95/02805, which wasfiled Jul. 18, 1995.

The present invention relates to a process for preparing vinyl esters ofcarbamic acid compounds. In particular, the present invention relates toa process for preparing compounds of this type, in which the reaction ofsecondary amines with carbon dioxide and acetylene compounds is carriedout in the presence of catalysts from the group of platinum metals.

The preparation of vinyl carbamates from vinyl chloroformate and aminesis a reaction which has been described in detail (R. A. Olofson et al.;THL 18, 1563-1566 (1977)).

Two variants are known for the preparation of vinyl chloroformatestarting from carbon oxychloride. On the one hand reaction with mercuryenolate (R. A. Olofson et at.; JOC, 43, 752, (1978)), and on the otherhand reaction with ethylene glycol to give ethylene glycolbischloroformate which is subsequently cleaved thermally to vinylchloroformate (L. H. Lee, JOC 30, 3943, (1965); U.S. Pat. No.2,377,095).

Besides the great safety precautions necessary when working with carbonoxychloride, there is a highly toxic risk in the use of organomercurycompounds.

Thermal elimination on ethylene glycol bischloroformate takes place onlywith poor selectivity and the formation of toxicologically objectionablebyproducts.

P. H. Dixneuf has described a synthesis of vinyl carbamates fromsecondary amines, carbon dioxide and acetylene (J. Org. Chem. 54, 1518(1989)). This entailed acetylene being dissolved in a solvent at -50° C.and reacted in an autoclave with carbon dioxide and a secondary aminewith catalysis by ruthenium trichloride at 80° C. to give the vinylcarbamate. The yields in this process are moderate.

J. of Organic Chemistry, Vol. 54, No. 7, p. 1518 (1989) relates to aprocess for preparing vinyl carbamates by reacting secondary amine withcarbon dioxide and acetylene, vinylacetylene or hexyne, with vinylcarbamates being obtained in the presence of ruthenium compounds with orwithout catalytic amounts of a free phosphine.

It is an object of the present invention to improve the process as knownfrom the prior art in such a way that high yields and/or highselectivity, preferably both, is achieved.

We have found that this object is achieved by a process for preparingvinyl carbamate compounds. These compounds have the formulae (I) and(II) ##STR1## where R¹ and R² each monovalent hydrocarbon radicals with1 to 6 carbon atoms, in particular alkyl or aryl- and/orcycloalkyl-substituted alkyl with 1 to 6 carbon atoms, aryl or alkyl-and/or cycloalkyl-substituted aryl with 6 to 10 carbon atoms andcycloalkyl or alkyl- and/or aryl-substituted cycloalkyl with 3 to 10carbon atoms, or

R¹ and R² form, together with the nitrogen to which they are bonded, aheterocyclic group with 5 to 7 ring members and I to 3 hetero atoms fromthe group of O, N, S,

R³ is alkyl or aralkyl with 1 to 6 carbon atoms, cycloalkyl with 3 to 10carbon atoms, aryl or alkaryl with 6 to 10 carbon atoms,

R⁴ is a divalent hydrocarbon radical with 1 to 10 carbon atoms, inparticular alkylene or aryl- and/or cycloalkyl-substituted alkylene with1 to 6 carbon atoms, arylene or alkyl- and/or cycloalkyl-substitutedarylene with 6 to 10 carbon atoms and cycloalkylene or alkyl- and/oraryl-substituted cycloalkylene with 3 to 10 carbon atoms, or

R⁴ and R¹ and/or R⁴ and R² or R⁴ and R² and R¹ form, with the particularnitrogen atoms to which they are bonded, a heterocyclic group with 5 to7 ring members and 1 to 3 hetero atoms from the group of O, N, S.

In the process, the appropriate secondary amines of the formulae (III)and (IV) ##STR2## where R¹, R², R³ and R⁴ have the abovementionedmeanings, are reacted with carbon dioxide and acetylenically unsaturatedcompounds of the formula (V)

    R.sup.3 -C↑CH                                        (V)

where R³ has the abovementioned meaning. This reaction takes place inthe presence of a compound of a metal from the platinum group, inparticular a ruthenium compound.

In this reaction, according to the invention process step (b) with orwithout process step (a), or, preferably both, are carried out:

(a) the acetylene compound is reinjected during the reaction;

(b) the reaction is carried out in the presence of a tertiary amine.

It has been found, surprisingly, that secondary amines can be reactedwith carbon dioxide and acetylene to give the vinyl carbamates indistinctly higher yields when there is continuous reinjection ofacetylene during the reaction and a tertiary amine is added to thereaction.

Amine Compounds

Particularly suitable amine compounds of the formulae (III) and (IV) are

piperidine compounds

morpholine compounds

piperazine compounds

dialkylamine compounds with 2 to 20 carbon atoms.

Preferred amine compounds are piperidine, N-ethylpiperidine, morpholineor diethylamine.

Acetylene Compounds

Preferred examples of the acetylene compounds which can be employedaccording to the invention are

acetylene

propyne

1-butyne

1-hexyne

phenylacetylene

vinylacetylene

diacetylene

Catalysts

Catalysts which can be employed are compounds of the platinum metals inall oxidation states, preferably compounds of ruthenium and of palladiumas such, eg. RuCl₃, Ru(acac)₃, Ru₃ (CO)₁₂ or PdCl₂. Various complexingagents can be employed for the compounds of the metals of the platinumgroup. Preferred are aliphatic and aromatic phosphines, phosphites andamines (eg. tributylphosphine, tripheniylphosphine, trimethyl phosphite,triethylamine). It is also possible according to the invention to usemultidentate ligands such as 1,2-bis(dimethylphosphino)ethane ortetramethylethylenediamine (TMEDA).

The platinum metal compound is employed in amounts of from 0.1 to 4 mol%, preferably from 0.5 to 2 mol %, based on amine group employed. Thecomplexing agent is preferably employed in 0.5 to 4 times the molaramount based on platinum metal compound employed.

Preferred Operating Conditions

The reaction is carried out at from 50° to 200° C., in particular from80° to 120° C. The pressure in the reaction is from 1 to 50 bar. Thereaction takes from 1 to 12 hours.

It is particularly advantageous first to react carbon dioxide with theamine and only then to add the acetylene compound to the reaction.

The amine can be employed as such, if it is liquid, or else as solutionin various organic solvents such as toluene, tetrahydrofuran oracetonitrile.

Tertiary Amines

The tertiary amines employed according to the invention preferably have3 to 30 carbon atoms in the hydrocarbon radicals. Examples of tertiaryamines which can be employed are

triethylamine

4-dimethylaminopyridine

DABCO (diazabicyclooctane)

1,8-bis(dimethylamino)naphthalene

trioctylamine.

Triethylamine is currently preferred.

The tertiary amines are employed in catalytic to stoichiometric amountsfor this purpose, with stoichiometric amounts being based on thesecondary amino groups in the compounds of the formula (III) or (IV)employed.

Isolation of the Vinyl Carbamate Compounds

The vinyl carbamate compounds formed in the process according to theinvention are isolated from the reaction mixture preferably by simpledistillation of the crude vinylation product.

Preferred embodiments of the invention are indicated in the dependentclaims and in the following examples.

EXAMPLE 1

75 g of piperidine and 1.5 g of ruthenium trichloride hydrate were addedto 75 g of acetonitrile and, at room temperature, 10 bar of carbondioxide were injected to constant pressure. The mixture was then heatedto 100° C. and acetylene was subsequently injected, up to a totalpressure of 20 bar, until the pressure was constant.

The reaction mixture was subsequently washed with aqueous hydrochloricacid, the acetonitrile was removed, and distillation was carried out.

The yield (mol % from secondary amine employed) of vinylN-piperidinecarboxylate was 63% of theory.

EXAMPLE 2

Morpholine was reacted with carbon dioxide and acetylene as inExample 1. The yield of vinyl N-morpholinecarboxylate after workup anddistillation was 49% of theory.

EXAMPLE 3

N-Ethylpiperazine was reacted with carbon dioxide and acetylene as inExample 1. After removal of the acetonitrile, the product was distilled.The yield of vinyl N-ethyl-N'-piperazinecarboxylate was 93% of theory.

EXAMPLE 4

Diethylamine was reacted with carbon dioxide and acetylene as inExample 1. The yield of vinyl N,N-diethylcarbamate after removal of theacetonitrile and distillation was 10% of theory.

EXAMPLE 5

Diethylamine was reacted in acetonitrile and 30 ml of triethylamine withcarbon dioxide and acetylene as in Example 1. The yield of vinylN,N-diethylcarbamate after workup and distillation was 75% of theory.

We claim:
 1. A process for preparing a vinyl carbamate compound of theformula (I) or (II) ##STR3## where each of R¹ and R² are monovalenthydrocarbon radicals having 1 to 6 carbon atoms; orR¹ and R², togetherwith the nitrogen to which they are bonded, form a heterocyclic groupwith 5 to 7 ring members and from 1 to 3 hetero atoms selected from O, Nand S; R³ is alkyl with 1 to 6 carbon atoms; cycloalkyl with 3 to 10carbon atoms; aryl or alkaryl with 6 to 10 carbon atoms; R⁴ is adivalent hydrocarbon radical with 1 to 10 carbon atoms; or R¹ and R⁴, R²and R⁴, and R¹ and R², together with the nitrogen atom to which they arebonded, form a heterocyclic group with from 5 to 7 ring members and from1 to 3 hetero atoms selected from O, N and S;said process comprisingreacting a secondary amine of the formula (III) or (IV) ##STR4## withcarbon dioxide and an acetylenically unsaturated compound of the formula(V)

    R.sup.3 -C↑CH                                        (V)

where R³ has the above mentioned meanings; said reaction being carriedout in the presence of a compound of a metal from the platinum group;said reaction being carried out in the presence of a tertiary amine; andwherein the acetylene compound is reinjected during the reaction.
 2. Aprocess as defined in claim 1, wherein the reaction is carried out at atemperature of from 50° to 200° C., a pressure of from 1 to 50 bar, andfor a duration of from 1 to 12 hours.
 3. A process as defined in claim1, wherein the reaction of the amine with carbon dioxide and acetyleneis carried out in the presence of Ru^(III) compounds.
 4. A process asdefined in claim 3, wherein the reaction of the amine with carbondioxide and acetylene compound is carried out in the presence ofruthenium trichloride as catalyst.
 5. A process as defined in claim 1,wherein the reaction of the amine with carbon dioxide and acetylenecompound is carried out in the presence of compounds of the platinummetals with the addition of complexing agents selected from phosphines,phosphites and amines.
 6. A process as defined in claim 1, wherein apiperidine compound, a morpholine compound, a piperazine compound or adialkylamine compound, is used as compound of the formula (III).
 7. Aprocess as defined in claim 1, further comprising adding a solvent tothe reaction mixture, said solvent being selected from the groupconsisting of toluene, tetrahydrofuran, dimethyl sulfoxide, acetonitrileand N-methylpyrrolidone.
 8. A process as defined in claim 1, wherein anexcess of acetylene compound of from 1.5 mol to 10 mol of acetylenecompound based on 1 mol of the secondary amine is used.
 9. A process asdefined in claim 1, wherein acetylene (R³ =H) is used as acetylenecompound.
 10. A process as defined in claim 1, wherein triethylamine isused as tertiary amine.
 11. A process as defined in claim 1, wherein thesecondary amine compound is first reacted with carbon dioxide andsubsequently the acetylene compound is added.
 12. A process as definedin claim 1, wherein the metal compound from the platinum group is aruthenium compound.
 13. A process as defined in claim 11, wherein from 1to 2 mol of carbon dioxide are reacted with the secondary amine under apressure of about 50 bar of carbon dioxide, and wherein 1 to 10 mol ofthe acetylenically unsaturated compound are used, and the reaction,following the addition of the ethylene compound, is allowed to proceedfor from 2 to 12 hours.
 14. A process as defined in claim 6, wherein thecompound of formula (III) is piperidine, morpholine or diethylamine.